How to waterproof your bathroom floor

Ash
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Project Overview

Water leaking into your floor and wall spaces can rot structural timbers and cause damage. We’ll show you the simple steps it takes to waterproof a bathroom floor without the mess.
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This D.I.Y. Advice is part of a series How to lay floor tiles

Step by Step Instructions

1 Clean the floor
2 Apply the primer
3 Silicone the gaps
4 Apply masking tape to the wall
5 Apply the waterproofing agent
6 Apply the waterproof membrane to joints
7 Waterproof the whole floor
8 Apply the last coat of waterproofing agent
  • Step 1. Clean the floor

    Before you start waterproofing it’s important that the floor is clean. Clear any dust and dirt away with a dustpan and broom.

  • Step 2. Apply the primer

    The easy way to apply your primer is to pour it into a bucket or roller tray first. Then using a paint roller, start in the back corner and work your way around the walls to a height of about 20cm. Then apply the primer to the whole bathroom floor.
  • Step 3. Silicone the gaps

    After the primer has dried, silicone seal all of the gaps between the floor and the wall and anywhere you find gaps in the floor. Use a paint scraper to remove any excess silicone. Then let the silicone dry for 24 hours before you start waterproofing. 

  • Step 4. Apply masking tape to the wall

    Apply masking tape around the wall to the level you want to make waterproof. In our case, we’re masking to the height of where the primer was applied. If you want to waterproof to the shower recess, your masking tape needs to be at a height of 1.8m. 

  • Step 5. Apply the waterproofing agent

    Start at the back corner of the bathroom. Use a roller to apply the waterproofing agent on the wall to the height of the masking tape. Then apply it around the width of the paint roller where the wall meets the floor.

  • Step 6. Apply the waterproof membrane to joints

    Cut the waterproof membrane into lengths of the bathroom walls. Lay the membrane down so that half is on the wall and the other half on the bathroom floor covering the crack. To stick the membrane down, use either a paint roller or brush to paint over it with the waterproofing agent. Repeat this until all of the gaps on the floor are covered with membrane and painted over. 

  • Step 7. Waterproof the whole floor

    After you have covered all of the membrane on the walls and bathroom floor with the waterproofing agent, paint the rest of the floor. Then leave it to dry for 24 hours.

  • Step 8. Apply the last coat of waterproofing agent

    After letting the waterproofing agent dry, apply a final coat of waterproofing to the walls and bathroom floor with a brush or roller. You’ll need to let this second coat dry another 24 hours before it’s ready.
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